Secondary metabolite and inorganic contents in Cystodytes sp. (Ascidiacea): temporal patterns and association with reproduction and growth
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Temporal variation is one of the least known components of defence production in marine organisms. Here we examined whether there is a predictable temporal pattern in the production of chemical and structural defences by a marine invertebrate. To assess the seasonal variation in chemical defence, we measured ascididemin, the main pyridoacridine alkaloid in the blue Mediterranean morph of the ascidian Cystodytes sp. Structural defence variability was assessed on the basis of colony ash content, as it contains mainly spicules. Ascididemin concentration and the colony ash content displayed an annual cycle, reaching a minimum in spring and peaking in summer. Cross-correlation analyses with existing data on growth and reproduction suggested a significant trade-off between investment in reproduction and the other biological parameters considered (growth, inorganic content and ascididemin concentration). Our results suggest that optimization of resource allocation, probably influenced by biotic interactions and physical factors, shaped the temporal trends observed in secondary metabolite concentration and inorganic content.
KeywordsBiological Parameter Total Organic Matter Structural Defence Inorganic Content Larval Release
Joseph R. Pawlik kindly made useful comments to improve this ms. Philippe Kerhervé (CEFREM) provided access to a 500°C oven. Diving assistance was provided by C. Menniti (University of Perpignan) and C. Palacin (University of Barcelona). F. Jamme helped with some laboratory work. This study was funded by the Interreg IIIA n. I3A-1-72-E program of the EU, by a Ministry of Education and Science/Fulbright grant to S.L-L., and the project CTM2004-05265 of the Spanish Government.
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